The presently disclosed embodiments are directed to processes for making phase change or solid ink used in ink jet system recording apparatuses (e.g., printer, copying machine, facsimile, word processor, plotter, and the like). More particularly, the embodiments pertain to the preparation of pigment or dye-based solid inks using a high shear in-line homogenizer with a rotor-stator style blade for improved dispersion. In addition, the in-line homogenizer uses multiple stages tooling and is installed outside of the vessel so that the homogenizers are not limited to specific mixing chamber geometries or vessel geometries.
Recording apparatuses using an ink jet system employ a recording method in which a liquid or fused solid ink is ejected as small droplets through a nozzle, slit, porous film, or the like, and deposited onto the surface of a recording material such as paper, cloth, or film to record letters or figures on the recording material. Such systems are advantageous because the apparatus is compact, inexpensive and noiseless. An ink for use in an ink jet recording apparatus mainly comprises a liquid, a coloring material and additives. Such ink is generally required to have properties including: the formation of a record having high-resolution and high-density uniform image without causing blotting or fogging on the recording material, the ability to be used without clogging nozzle tips due to drying of the ink, the facilitation of ejection responsibility and stability so that the nozzle tip is kept in good condition, the exhibition of good drying property, the formation of an image with good fastness, and the high stability to ensure long-term storage.
Additives that may be added to the dispersed coloring material and the liquid include a surfactant or a fixing agent. A surfactant may added to lower the surface tension of the liquid to obtain acceptable levels of transfer, coating spread and adhesion. A fixing agent may be added to prevent permeation of the coloring material in the ink. Other additives may also be included in the ink, such as antioxidants, viscosity modifiers, clarifiers, conductivity agents and dyes used as auxiliary colorants, as disclosed in U.S. Pat. No. 6,878,198 and U.S. Patent Publication No. 20050113482, the disclosures of each of which are totally incorporated herein by reference.
Factors such as droplet and particle size may have effect on whether the ink formed will have the desired properties. Pigment solids should be small and evenly dispersed to ensure that the droplets will be small and uniformly emulsified. Providing uniformly dispersed pigments in small droplets may result in higher particle surface area, and thus, more brilliant color and smoother finish. Providing smaller particle and droplet size may also further facilitate better penetration into the recording material so that the image created dries better, is more resistant to rubbing or bleeding and may impart higher stability for long-term storage. The quality of the product ink may be controlled by “Filter Tests,” e.g., a ink-making process is satisfactory if the product ink passes such a “Filter Test.”
The finished ink is evaluated by a number of characterization tests including viscosity, thermo-gravimetric analyses, various filtration tests and print quality tests. The filtration tests were designed to emulate flow of molten ink through a printer head. For example, one of the filtration tests conducted involves measuring 100 grams of molten ink at fixed temperature (105-135° C.) and pressure (15 psig) as the ink passes through a 0.45 μm glass fiber membrane per unit time. An ink which meets the specification will pass through the 0.45 μm filter membrane in less than 5 minutes. Inks which are not homogenized adequately or filtered properly will not pass through under 5 minutes.
Although different types of ink may be used with ink jet systems, phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
In general, phase change or solid inks (sometimes also referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference. Phase change inks have also been used for applications such as postal marking and industrial marking and labeling.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible pigment colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
U.S. Pat. No. 4,889,560 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink carrier composition combined with a compatible colorant to form a phase change ink composition. A thin film of substantially uniform thickness of that phase change ink carrier composition, and the ink produced therefrom, has a high degree of lightness and chroma. The thin films of a substantially uniform thickness of the ink composition are also rectilinearly light transmissive. The carrier composition is preferably a fatty amide-containing compound.
U.S. Pat. No. 4,889,761 (Titterington et al.), the disclosure of which is totally incorporated herein by reference, discloses a method for producing a light-transmissive phase change ink printed substrate is described which comprises providing a substrate, and then printing on at least one surface of the substrate a predetermined pattern of a light-transmissive phase change ink which initially transmits light in a non-rectilinear path. The pattern of solidified phase change ink is then reoriented to form an ink layer of substantially uniform thickness. This ink layer will, in turn, produce an image which then will transmit light in a substantially rectilinear path. In one aspect of the invention, the substrate is light transmissive, and the reoriented printed substrate exhibits a high degree of lightness and chroma, and transmits light in a substantially rectilinear path. In this way, the reoriented printed substrate can be used in a projection device to project an image containing clear, saturated colors.
U.S. Pat. No. 5,372,852 (Titterington et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition that is indirectly applied to a substrate by raising the temperature of the phase change ink composition to form a liquid phase change ink composition, applying droplets of the phase change ink composition in a liquid phase to a liquid intermediate transfer surface on a solid support in a pattern using a device such as an ink jet print head, solidifying the phase change ink composition on the liquid intermediate transfer surface, transferring the phase change ink composition from the liquid intermediate transfer surface to the substrate, and fixing the phase change ink composition to the substrate. The phase change ink composition is malleable when the ink is transferred from the intermediate transfer surface to the substrate and is ductile after the ink has been transferred to the substrate and cooled to ambient temperature to preclude the ink from crumbling and cracking.
U.S. Pat. No. 5,621,022 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition wherein the ink composition utilizes polymeric dyes in combination with a selected phase change ink carrier composition.
U.S. Pat. No. 5,782,966 (Bui et al.), the disclosure of which is totally incorporated herein by reference, discloses resins and waxes made by reacting selected nucleophiles, including alcohols and/or amines, with an isocyanate. The order of addition of the isocyanate and the different nucleophiles can tailor the distribution of di-urethane, mixed urethane/urea, and/or di-urea molecules in the final resin product. The isocyanate-derived resin and wax materials are useful as ingredients as phase change ink carrier compositions used to make phase change ink jet inks.
U.S. Pat. No. 5,902,841 (Jaeger et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition wherein the ink composition utilizes colorant in combination with a selected phase change ink carrier composition containing at least one hydroxy-functional fatty amide compound.
U.S. Pat. No. 5,994,453 (Banning et al.), the disclosure of which is totally incorporated herein by reference, discloses phase change carrier compositions made from the combination of at least one urethane resin; at least one urethane/urea resin; at least one mono-amide; and at least one polyethylene wax. The order of addition of the reactants to form the reactant product urethane resin and urethane/urea resin permits the tailoring or design engineering of desired properties.
U.S. Pat. No. 6,174,937 (Banning et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink comprising a material of the

wherein X.sub.1, X.sub.2, X.sub.3, and X.sub.4 are segments comprising atoms selected from groups V and VI of the periodic table; wherein at least one R.sub.1 and R.sub.5 comprises at least 37 carbon units; and wherein R.sub.2, R.sub.3, and R.sub.4 each comprise at least one carbon unit. The invention further encompasses a composition of matter, as well as methods of reducing coefficients of friction of phase change ink formulations.
U.S. Pat. No. 6,309,453 (Banning et al.), the disclosure of which is totally incorporated herein by reference, discloses colorless compounds having a central core and at least two arms extending from the core. The core can comprise one or more atoms. The at least two arms have the

In such formula, Z is a segment of one or more atoms; j is an integer from 1 to about 300 and can be different at one of the at least two arms than at another of the at least two arms; Q is an alkyl or aryl group and can vary amongst different alkyl and aryl groups within the colorless compound; and n is an integer greater than 1 and can be different at one of the at least two arms than at another of the at least two arms. In other aspects, the invention encompasses phase change inks incorporating the above-described colorless compound as toughening agent, and methods of printing with such phase change inks. The invention further includes a solid ink comprising a colorant and a colorless compound of the

In such formula, X is a single atom corresponding to N or O; Z.sub.1 and Z.sub.2 are substituents comprising one or more atoms, and can be the same as one another or different from one another; and j is an integer from 1 to about 50.
U.S. Pat. No. 6,380,423 (Banning et al.), the disclosure of which is totally incorporated herein by reference, discloses colorless compounds having a central core and at least two arms extending from the core. The core can comprise one or more atoms. The at least two arms have the

In such formula, Z is a segment of one or more atoms; j is an integer from 1 to about 300 and can be different at one of the at least two arms than at another of the at least two arms; Q is an alkyl or aryl group and can vary amongst different alkyl and aryl groups within the colorless compound; and n is an integer greater than 1 and can be different at one of the at least two arms than at another of the at least two arms. In other aspects, the invention encompasses phase change inks incorporating the above-described colorless compound as toughening agent, and methods of printing with such phase change inks. The invention further includes a solid ink comprising a colorant and a colorless compound of the

In such formula, X is a single atom corresponding to N or O; Z.sub.1 and Z.sub.2 are substituents comprising one or more atoms, and can be the same as one another or different from one another; and j is an integer from 1 to about 50.
U.S. Pat. No. 5,221,335 (Williams et al.), the disclosure of which is totally incorporated herein by reference, discloses a stabilized pigmented hot melt ink containing a thermoplastic vehicle, a coloring pigment, and a dispersion-stabilizing agent to inhibit settling or agglomeration of the pigment when the ink is molten, comprising 1.5 to 20 weight percent of a nitrogen-modified acrylate polymer. A preferred dispersion-stabilizing agent is the nitrogen-modified methacrylate polymer marketed by Rohm & Haas Co. as Plexol 1525.
U.S. Pat. No. 5,800,600 (Lima-Marquez et al.), the disclosure of which is totally incorporated herein by reference, discloses a solid ink jet ink composition which is suitable for hot melt applications having a carrier having an electrical resistivity of at least 10.sup.8 Ohm·cm, insoluble marking particles, and a particle charging agent dispersed in it. The marking particle may be a pigment, an insoluble dyestuff, a polymer, or mixture thereof. The particle charging agent may be a metal soap, a fatty acid, lecithin, an organic phosphorous compound, a succinimide, a sulfosuccinate, petroleum sulfonates, a soluble or partially soluble resin such as a modified rosin ester, an acrylic, a vinyl, a hydrocarbon, or a mixture thereof. The solid ink jet ink composition may further include a viscosity controller. The ink may be capable of being heated to 155.degree. C. and have at that temperature a viscosity of between 5 to 150 centipoise.
In order to make inks that possess the desired characteristics, various techniques have been proposed. For example, U.S. Pat. No. 6,858,070 discloses the use of single high shear mixers to manufacture ink, the entire disclosure thereof being incorporated herein by reference. Dye-based solid inks are commonly manufactured by dispersing the dyes and other ink components into molten wax in mixing chambers, such as feed tanks, using batch mixers with saw-tooth style or other single-stage “in-tank” impellers. Although saw-tooth style and other single-stage high speed in-tank batch mixers are adequate for dispersion of dyes in molten wax, they do not provide the adequate shear rate necessary for breaking up pigment agglomerates to submicron sized particles. Another technique used to manufacture ink jet inks involves homogenizers that have rotor-stator style in-tank batch mixers. This batch process has been developed for preparing pigment-based solid ink by dispersing the pigments and other ingredients into molten wax in a type of mixing chamber using a rotor-stator style in-tank, high-shear batch mixer. These rotor-stator style batch mixers are designed for specific tank geometry, however, and typically can only accept one set of rotor-stator tooling. This makes the rotor-stator style batch mixers less flexible and more expensive to use.
In addition, in-tank batch mixers do not permit the process to be set up in “discrete passes” configuration, which produces narrow particle size distribution and allows all of the materials to be processed by the in-line homogenizer and its rotor-stator tooling between passes.
Thus, while known processes and systems are suitable for their intended purposes, a need remains for methods for preparing phase change or solid inks in a system that is more flexible and has more enhanced homogenization capabilities.